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ASEAN Journal on Science and Technology for Development

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Published by Universitas Gadjah Mada

ISSN : 22249028 EISSN : 22249028 DOI : -

Core Subject : Science, Education, Engineering,

Biochemistry, Genetics & Molecular Biology Chemical Engineering, Chemistry & Bioengineering Computer Science & IT Mathematics

The coverage is focused on, but not limited to, the main areas of activity of ASEAN COST, namely: Biotechnology, Non-Conventional Energy Research, Materials Science and Technology, Marine Sciences, Meteorology and Geophysics, Food Science and Technology, Microelectronics and Information Technology, Space Applications, and Science and Technology Policy, Infrastructure and Resources Development.

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Articles 477 Documents

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Effect of fly ash particle reinfo rcement on microstructure, porosity and hardness in Al-(Si-Mg) cast composites M.B. Harun; S.R. Shamsudin; H. Yazid; Z. Selamat; M.S. Sattar; M. Jalil
ASEAN Journal on Science and Technology for Development Vol. 23 No. 1-2 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The microstructure of cast Al-4Si-Mg reinforcedwith fly ash particles at various particlecontents has been studied. The composites were fabricated by stir casting process andcharacterized by optical microscopy, image analyzer, scanning electron microscopy and hardness measurements. The results showed that particle contents affected to the presence oforosities and hardness of the composites. It was observed that increasing the fly ash contentincrease the porosity in the composites, with the matrix alloy reinforced with 15 wt.% of fly ash particles having the highest porosity and lowest hardness.

Detection of antifungal compounds in Arabidopsis thaliana and brassica oleracea by thin layer chromatography . K.P. Chong; J.W. Mansfield; M.H. Bennet; J.F. Rossiter
ASEAN Journal on Science and Technology for Development Vol. 23 No. 1-2 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Thin Layer Chromatography (TLC) was applied to detect antifungal compounds both in Arabidopsis thaliana and Brassica oleracea after elicited by various biotic and abiotic elicitors.From TLC bioassays the only strong zone of inhibition detected after challenged by Pseudomonas syringae pv.maculicola was from Arabidopsis tissue and later confirmed by spectrophotometry as camalexin but no corresponding phytoalexin was found in broccoli leaf.

G-jitter induc ed free convection over a vertical flat plate Nawaf H. Saeid
ASEAN Journal on Science and Technology for Development Vol. 23 No. 1-2 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The effect of the periodic oscillation of the gravitational field, known as g-jitter, on the free convection from a vertical plate is investigated in the present paper. The problem has been simplified by the laminar boundary layer and Boussinesq approximations. The fully implicit finite-difference scheme is used to solve the dimensionless system of the governing equations.The results for laminar flow of air (Pr = 0.72) and water (Pr = 7.00) are presented for different values of the amplitudes and frequencies of the g-jitter. The results presented show the steady periodic variation of Nusselt number and the friction coefficient with the amplitude and frequency of the gravitational acceleration oscillation. It is found that the Prandtl number as well as the amplitude and the frequency of the oscillating gravitational acceleration affect considerably the periodic oscillation of the Nusselt number and the skin friction on the vertical plate.

Optical Resonance of A Three-Level System in Semiconductor Quantum Dots Nguyen Van Hieu; Nguyen Bich Ha
ASEAN Journal on Science and Technology for Development Vol. 23 No. 3 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The optical resonance of a three-level system of the strongly correlated electrons in the twolevel semiconductor quantum dot interacting with the linearly polarized monochromatic electromagnetic radiation is studied. With the application of the Green function method the expressions of the state vectors and the energies of the stationary states of the system in the regime of the optical resonance are derived. The Rabi oscillations of the electron populations at different levels as well as the Rabi splitting of the peaks in the photon emission spectra are investigated.PACS numbers: 71.35.-y, 78.55.-m, 78.67.Hc

Effectiveness of Selected Entomopathogenic Fungi in Packed Rice Grain at Room Temperature Against Corcyra Cephalonica Stainton Hendrawan Samodra; Yusof Bin Ibrahim
ASEAN Journal on Science and Technology for Development Vol. 23 No. 3 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Eight isolates of entomopathogenic fungi were evaluated as dried conidia against the rice moth, Corcyra cephalonica. In bioassays two isolates of Beauveria bassiana (BbGc and BbPs) and one isolate of Metarhizium anisopliae (MaPs) consistently gave high mortality to C. cephalonica larvae. Formulations in either kaolin, talc or tapioca flour (20 % w/w a.i.) thoroughly mixed with long grain rice in plastic cups (8 cm diameter by 5 cm) gave complete larval mortality by the 12th day of treatment. However, in general those formulated in kaolin and talc were more efficacious and faster to kill compared to those formulated in tapioca flour or the unformulated control. Even at the lowest rate of 0.05 g BbGc in kaolin provided 100% mortality 7 days after introduction compared with other dust formulations. Isolate BbGc in kaolin and talc administered at 0.4 g a.i. in 200 g rice packed in plastic kept at room temperature provided protection against the rice moth up to 4 months of storage. Larval mortality in excess of 90% was obtained 15 days after introduction. Formulations of MaPs was effective only within the first month of storage beyond which infectivity rapidly declined.

Effects of Habitat Fragmentation on Genetic Diversity in Cycas Balansae (Cycadaceae) Nguyen Minh Tam; Nguyen T. Phuong Trang; Vu T. Ha Giang; L. Triest Triest
ASEAN Journal on Science and Technology for Development Vol. 23 No. 3 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Habitat fragmentation is a serious threat to species survival. In Vietnam, Cycas balansae has been considered as threatened species because of the reduction and fragmentation of its habitats and over-exploitation. We assessed genetic variability and the pattern of population structure among six populations sampled in four provinces: Hoa Binh, Ha Nam, Ninh Binh and Quang Ninh. Polyacrylamide gel electrophoresis was performed on leaf tissues from 152 individuals representing 6 populations of C. balansae. Six of twelve enzyme systems were used to estimate genetic diversity at population and species levels. Eleven loci were examined. The allozyme data showed high levels of genetic diversity within all populations, ranging from 0.538 in Ba Sao to 0.628 in Tan Dan (average 0.576). The maintenance of high levels of expected heterozygosity (average 0.571) and low in observed heterozygosity (average 0.347) might be related to great heterozygote deficiency and increased frequencies of rare alleles. Genetic differentiation among populations was low (Dst = 0.036 and Gst = 0.064), indicating high level of gene flow (Nm = 3.22). Isolation by geographical distance was observed, however, no significant relationship between genetic distances and geographical distances was recorded. Our studies suggest small population sizes of cycads brought about by fragmentation of its habitats, over-exploitation, and increasing number of inbred individuals within populations.

Crossflow Ultrafiltration for Removing Direct-15 Dye from Wastewater of Textile Industry A.L. Ahmad; S.W. Puasa; S. Abiding
ASEAN Journal on Science and Technology for Development Vol. 23 No. 3 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Ultrafiltration membrane was used to treat the effluent from textile industries. Crossflow ultrafiltration using GN polymeric membrane was used to remove the dye from textile effluent. A synthetic textile effluent of Direct-15 dye was used. The study focused through the effect of feed concentration, transmembrane pressure and solution’s pH on the permeate flux and percentage of dye removal were investigated. Dye concentration had significant effects on flux values. Under the fixed pressures and pH, the flux decreased while the dye rejection increased with increasing feed concentration. Transmembrane pressure also had significant effect on flux values. Under the fixed feed concentration and pH, the flux increased while dye rejection decreased with increasing pressure. Experiment data showed that the highest flux was observed at pH 4 (acidic condition) while the highest dye removal observed at pH 7. Data collection could be used to improve the effectiveness of dye removal from textile industry wastewater using membrane technology.

A Fuzzy Logic Based Method for Analysing Test Results Le Xuan Vinh; Tran Hong Quan
ASEAN Journal on Science and Technology for Development Vol. 23 No. 3 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Network operators must perform many tasks to ensure smooth operation of the network, such as planning, monitoring, etc. Among those tasks, regular testing of network performance, network errors and troubleshooting is very important. Meaningful test results will allow the operators to evaluate network performanceof any shortcomings and to better plan for network upgrade. Due to the diverse and mainly unquantifiable nature of network testing results, there is a needs to develop a method for systematically and rigorously analysing these results.In this paper, we present STAM (System Test-result Analysis Method) which employs a bottom-up hierarchical processing approach using Fuzzy logic. STAM is capable of combining all test results into a quantitative description of the network performance in terms of network stability, the significance of various network erros, performance of each function blocks within the network. The validity of this method has been successfully demonstrated in assisting the testing of a VoIP system at the Research Instiute of Post and Telecoms in Vietnam.The paper is organized as follows. The first section gives an overview of fuzzy logic theory the concepts of which will be used in the development of STAM. The next section describes STAM. The last section, demonstrating STAM’s capability, presents a success story in which STAM is successfully applied.

Role of Sawdust in the Removal of Iron from Aqueous Solution H.B. Senin; O. Subhi; R. Rosliza; N. Kancono; M.S. Azhar; S. Hasiah; W.B. Wan Nik
ASEAN Journal on Science and Technology for Development Vol. 23 No. 3 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Sawdust, inexpensive material has been utilized as an absorbent for the removal of iron from aqueous solution for their safe disposal. The adsorption experiments of untreated sawdust (SD) and treated sawdust (SDC) have been carried out at room temperature using the batch test. The Langmuir and Freundlich isotherms were used to observe sorption phenomena of sawdust in the removal of iron. The results indicate that the sawdust was capable in removing iron in aqueous solution. The results have shown that the Langmuir isotherm was found well fitted into the experimental data as compared to the Freundlich isotherm. It was found that, chemisorptions and physisorption were the prime mechanism for the process of adsorption to occur between the sawdust and iron. The results also proved that the acid sulphuric treated sawdust is much better than that of untreated sawdust as an adsorbent for iron.

Timing Synchronization for Mc-Cdma Systems Using a Time-Multiplexed Synchronization Channel Pham Hong Ky; Nguyen Duc Long
ASEAN Journal on Science and Technology for Development Vol. 23 No. 3 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

In this paper, we present a synchronization algorithm for Multi-Carrier CDMA (MC-CDMA) systems using a time-multiplexed synchronization channel. The simulations results show that a system using proposed algorithm has much higher timing detection probability than using other algorithms, especially in exponential decay multipath fading.

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